Any reason not to up a TBI fuel pressure?

[toehead]

I'm running a geo metro throttle body on my GL1000. It contains a stock fuel pressure regulator set to 15-20 lbs and a 60 lb injector (flow rated at 43.5 lbs).

I have the bike running great at idle and midrange, but when sizing the throttle body any injector I didn't account for the low fuel pressure. With the 15 psi, I run into 100% duty cycle at about 4500 RPM (out of 9000 redline). If I get the injector to flow at least the rated 60 lbs, I can support my engine.

I put a shim on the FPR spring and bumped the pressure to 55 lbs with no apparent leaks but I have yet to try to start it.

My question: Is there a practical upper limit to the PSI you can use on a TBI injector? Megamanual only says to stay under 70 psi. I am using RUBBER fuel injection hoses (only about a foot or so total length since this is a bike)

Is there any downside to running 55 PSI? I can also back it off by playing with the shim thickness.

I appreciate any feedback.

[slow_hemi6]

Opening and closing issues can come up if you go beyond the rated pressure. Those injectors in the metro look like bosch. I have run bosch tbi injectors at 3 bar because I have found them flow rated by bosch at 3 bar so why not. I would look at getting a junkyard dodge 90 - 95 tbi injector 0280150665 and see if it fits in your tbi. They look pretty much the same to me and would flow a lot more. Bosch have them at 1030ccm at 3 bar and your 0280150661 at 630 at 3 bar.

[toehead]

Thanks for the reply. It is indeed a bosch injector. It's good to know that somebody else has run TBI injectors at the rated pressure, instead of the really low pressures most OEMs run.

A 60 lb injector should be plenty for my application (with margin), if I can get it to flow @60 lbs I'll also go junkyard shopping for plan B!

[toehead]

55 lbs is too much. It started but quickly flooded due to injector closing issues.

I backed it of to ~40 lbs and that seems just about right.

[slow_hemi6]

I only ever tried them at 3 bar which is 43psi. That was also the best my pump could do.